1. Technical Field
The present invention relates to a piezoelectric thin film element having a piezoelectric thin film made of lithium potassium sodium niobate, and a piezoelectric thin film device including the same.
2. Description of Related Art
A piezoelectric body is processed into various piezoelectric elements according to the purpose of use, and is broadly utilized particularly as a functional electronic component such as an actuator for adding voltage to cause deformation to occur, and a sensor for generating voltage from the deformation of the elements reversely. As the piezoelectric body utilized for the purpose of the actuator and the sensor, a lead-based dielectric material having great piezoelectric characteristics, and particularly a Pb(Zr1-xTix)O3-based perovskite type ferroelectric material called PZT has been broadly used, and normally is formed by sintering an oxide material composed of individual elements. Further, in recent years, it is desired to develop the piezoelectric body not containing lead in consideration of an environment, and development of lithium potassium sodium niobate (general formula: (NaxKyLiz)NbO3 (0≦x≦1, 0≦y≦1, 0≦z≦0.2, x+y+z=1), etc, has been accelerated. The lithium potassium sodium niobate has the piezoelectric characteristics comparable to PZT, and therefore is expected as an important candidate of a non-lead piezoelectric material.
Meanwhile, at present, as a smaller size and higher performance of each kind of electronic component are accelerated, a smaller-sized piezoelectric element having higher performance is strongly requested. However, regarding the piezoelectric material manufactured by a conventional manufacturing method, by mainly a sintering method, when its thickness is 10 μm or less, the size of the piezoelectric material becomes close to sizes of crystal grains that constitute the material, and an influence thereof can not be ignored. Therefore, there is a problem that variation and deterioration of the characteristics become conspicuous. Accordingly, in order to avoid such a problem, in recent years, a method of forming the piezoelectric material using a thin film technique, etc, replacing the sintering method has been studied.
In recent years, a PZT thin film formed by RF sputtering is put to practical use as an actuator for a head of a highly precise high speed ink jet printer and a small-sized inexpensive Gyro sensor (for example, see patent document 1 and non-patent document 1). Further, patent document 2 also discloses a piezoelectric thin film element using a piezoelectric thin film made of lithium potassium sodium niobate and not using lead.
(Prior Art Document)
(Patent Document)
(Patent Document 1)
    Japanese Patent Laid Open Publication No. 10-286953(Patent Document 2)    Japanese Patent Laid Open Publication No. 2007-19302    (Non-patent document 1) Supervised by Kiyoshi Nakamura Higher performance of piezoelectric material and advanced applied technology (published by science & technology in 2007)